Feeling sleepy during the day is often brushed off as a normal part of modern life. However, growing evidence suggests that daytime sleepiness is far more common, and more disruptive, than many people realize. Surveys show that about 70% of adults in the United States struggle with sleepiness daily, meaning this problem extends well beyond people with diagnosed sleep disorders.
Sleepiness is not just about feeling tired. It can affect how we think, feel, work, and interact with others. According to a national survey conducted by the American Academy of Sleep Medicine, people most often report that sleepiness affects their mood, stress levels, and work productivity. Many also say it interferes with their physical health, exercise routines, relationships, and even driving safety. These findings highlight that sleepiness is not a minor inconvenience, it is a widespread issue with real consequences for daily life
Staying alert during the day depends on several systems in the brain working together. One system builds up a natural need for sleep the longer we stay awake, similar to pressure slowly increasing in a balloon. Another system acts like an internal clock, helping the body know when it is time to be awake and when it is time to sleep. A third system helps keep the brain alert and engaged during the day.
When these systems are working well, we feel awake and focused. But when they fall out of balance, daytime sleepiness can take over. Not getting enough sleep, sleeping poorly, or keeping irregular sleep schedules can all increase the body’s drive for sleep. Sleeping at times that conflict with the body’s internal clock, such as during shift work or frequent late nights, can further weaken alertness during the day.
Certain brain chemicals also play an important role in staying awake. When these wake-promoting signals are disrupted, the brain may struggle to maintain steady alertness, even if a person spends enough time in bed. The result is ongoing sleepiness that does not resolve with short naps or caffeine.
Many common sleep disorders affect the same systems that regulate alertness. For example, sleep apnea repeatedly disrupts sleep throughout the night, preventing the brain from getting the deep, restorative rest it needs. Insomnia can lead to chronic sleep loss, even when people spend many hours trying to sleep. Circadian rhythm disorders occur when sleep schedules are out of sync with the body’s natural clock, making it hard to feel awake at socially required times. Other conditions, such as narcolepsy, directly affect the brain’s ability to stay awake.
Despite different causes, these conditions often lead to similar daytime effects. People may have trouble concentrating, react more slowly, feel emotionally overwhelmed, or become irritable. These effects help explain why survey respondents commonly report problems with mood, stress, productivity, and relationships. Adults between the ages of 25 and 44 were especially likely to say sleepiness affected their relationships, suggesting that this life stage, which is often marked by work demands and family responsibilities, may be particularly vulnerable to the effects of poor sleep.
Daytime sleepiness can affect far more than just energy levels. People may find it harder to focus at work, manage stress, or stay emotionally balanced. Tasks that once felt routine may take longer or feel overwhelming. Over time, this can strain relationships at home and work.
Many people also underestimate how much sleepiness affects safety. Feeling drowsy slows reaction time and increases the risk of brief “microsleeps,” especially during monotonous activities like driving. Research has consistently linked daytime sleepiness to higher rates of car accidents, workplace injuries, and errors in complex tasks.
The fact that most adults report daily sleepiness suggests that poor sleep is not just an individual issue, and rather a population-level concern. Many people normalize feeling tired and rely on caffeine or energy drinks to push through the day, without realizing that ongoing sleepiness may signal an underlying problem. This normalization can delay evaluation and treatment, allowing the effects of sleepiness to accumulate over time.
Improving sleep health has the potential to benefit not only individual well-being but also productivity, emotional health, and public safety. Identifying sleep problems early and addressing them effectively could reduce accidents, improve mental health, and enhance overall quality of life.
Daytime sleepiness affects the majority of adults in the United States and interferes with many aspects of daily life, from mood and stress to work performance and safety. Understanding why sleepiness occurs and recognizing that it is often a sign of disrupted sleep rather than a personal failing, is an important step toward better health. Addressing sleepiness effectively with the help of a physician can improve not only how people sleep, but also how they feel, function, and engage with the world around them.
Slater, Gemma, and Joerg Steier. “Excessive daytime sleepiness in sleep disorders.” Journal of thoracic disease 4,6 (2012): 608-16. doi:10.3978/j.issn.2072-1439.2012.10.07
American Academy of Sleep Medicine (AASM), news release, Nov. 17, 2025